Isoxazole synthesis

A 1 1 adduct from diphenylsulfilimine and a benzoylacetylene underwent an intramolecular cyclization reaction to give an isoxazole in good yield (equation 40). Similarly, the 1 1 adduct from iodoazide and chalcone gave 3,5-diphenylisoxazole (equation 41). These two approaches to regiospecific isoxazole synthesis are of little practical significance. Additional examples of the (OCCCN) reaction are given in equations (42) and (43). 

Furoic acids — see Furancarboxylic acids Furo[3,4-d]isothiazole-4,6-dione, dihydrosynthesis, 6, 999 Furo[2,3-d]isoxazoles synthesis, 5, 148 Furo[3,2-d]isoxazoles synthesis, 6, 997 Furo[3,4-d]isoxazoles... 

Isoxazolo[5,4-d]isoxazole, 3a,6a-dihydro-structure, 6, 975 synthesis, 6, 1018 Isoxazoloisoxazoles synthesis, 3, 41 Isoxazoio[2,3-h]isoxazoies synthesis, 6, 1001 Isoxazolo[4,5-d]isoxazoles synthesis, 6, 989, 997... 

Fig. 15 Microwave-assisted isoxazole synthesis via on resin [3-1-2] cycioaddition. Reagents and conditions a 1-nitrobutane, DMTMM, DMAP, MeCN, THE, MW 80 °C, 5 min, open vessel b TEA CH2CI2 (5 95), rt, 20 min...

As for the solid support, several polymer-supported amines were tested (Fig. 2). For either the pyrazole and isoxazole synthesis, the best results were given by aniline-functionalized cellulose, which has also the advantage of a relatively low cost. For the 2-aminopyrimidine library, polystyrene-based piperazine and piperidine gave products with a much higher purity compared with other secondary non-cyclic or primary amines, hi both cases, the resins could be reused for up to four times before degradation in their behavior was observed. This reusability could be further enhanced (up to 10 cycles for cellulose-based aniline) when the microwave-assisted protocols were used. 

Brooks, D. A. Claisen Isoxazole Synthesis In Name Reactions in Heterocyclic Chemistry, Li, J. J. Corey, E. J., Eds. Wiley Sons Hoboken, NJ, 2005, 220-224. (Review). 

Isosteric equivalence, 77, 149 benzene and thiophene, 52 carbon and nitrogen, 399 Isothiouronium salts, as source of thiols, 44 Isothipendyl, 430 Isoxazole synthesis, 126 Isoxsuprine, 69 Ivanov reagent, 92, 93... 

Rj, R2 = atKyt or u-aacyi (see pyrazole and isoxazole synthesis. Chapter 4, and pyrimidine synthesis, Chapter 10)... 

The other important isoxazole synthesis involves the concerted [3+2] cycloaddition reaction of nitrile oxides 4.18 with either alkynes 4.19 or alkyne equivalents 4.20. 

Besides the mild conditions and excellent chemo- and regioselectivity the scope of this one-pot coupling-cycloaddition isoxazole synthesis is fairly broad. Due to acid chlorides as halide coupling partners, amines and hydroxy groups inevitably need to be protected prior to the reaction. Therefore, the use of acid chlorides 7 is principally limited to (hetero)aromatic compounds and derivatives without ot-hydrogen atoms. As an exception, the cyclopropyl group is tolerated as a... 

Interest in this class of heterocyclic compounds is well documented by many different applications, especially in the pharmacological domain. The development of new methodologies for facile isoxazole synthesis enhances even more the attractiveness of this system as a platform for the synthesis of complex molecules. 

---